- Total Synthesis of Unsymmetrically Oxidized Nuphar Thioalkaloids via Copper-Catalyzed Thiolane Assembly
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An asymmetric total synthesis of (+)-6-hydroxythiobinupharidine (1b) and (-)-6-hydroxythionuphlutine (2b), a set of hemiaminal containing dimeric sesquiterpenes isolated from yellow water lilies of the Nuphar genus, is described. The central bis-spirocyclic tetrahydrothiophene ring was forged through the Stevens rearrangement of a sulfonium ylide, generated in situ from the coupling of a copper-carbene with a spirocyclic thietane. This strategy diverges both from the proposed biosynthesis1 and previous syntheses of this family of alkaloids,2,3 all of which employ dimerization of symmetric monomers to form the aforementioned thiaspirane. The coupling of unsymmetrical monomers allowed access to the unsymmetrically oxidized product 2b for the first time.
- Lacharity, Jacob J.,Fournier, Jeremy,Lu, Ping,Mailyan, Artur K.,Herrmann, Aaron T.,Zakarian, Armen
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p. 13272 - 13275
(2017/10/05)
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- Synthesis of (-)-neothiobinupharidine
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An eight step, asymmetric synthesis of a dimeric thiaspirane nuphar alkaloid from 3-methyl-2-cyclo-pentenone is reported. The brevity of the route relies on a useful procedure for tandem reductive allylation of cyclopentenones, as well as the minimization of redox manipulations and other functional group interconversions. The distribution of products that arise from spontaneous dimerization points to a more complex biosynthesis.
- Jansen, Daniel J.,Shenvi, Ryan A.
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p. 1209 - 1212
(2013/03/28)
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- Crude drugs from aquatic plants. VI. On the alkaloid constituents of Chinese Nupharis Rhizoma, the dried rhizoma of Nuphar pumilum (TIMM.) DC. (Nymphaceae) : Structures and rearrangement reaction of thiohemiaminal type nuphar alkaloids
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From Chinese Nupharis Rhizoma, the dried rhizoma of Nuphar pumilum (TIMM.) DC. (Nymphaceae), four thiohemiaminal type nuphar alkaloids with potent immuno-suppressive activity, 6-hydroxythiobinupharidine, 6,6′-dihydroxythiobinupharidine, 6-hydroxythionuphlutine B, 6′-hydroxythionuphlutine B, have been isolated together with nine inactive nuphar alkaloids. The configurations of the 6- and 6′-hydroxyl groups in those thiohemiaminal type nuphar alkaloids were confirmed on the basis of their 2D-NMR analysis. During the course of chemical elucidation of those thiaspirane type dimeric sesquiterpene alkaloids, new rearrangement reaction of the thiaspirane ring in thiohemiaminal type alkaloids with 6-hydroxyl group was found and the reaction pathway was discussed. By using this rearrangement reaction, 6-hydroxythionuphlutine B was chemically related with 6-hydroxythiobinupharidine, so that the absolute stereostructures of thionuphlutine B and its related compounds such as 6-hydroxythionuphlutine B, 6′-hydroxythionuphlutine B, and thionuphlutine B β-sulfoxide, were characterized.
- Yoshikawa, Masayuki,Murakami, Toshiyuki,Wakao, Shuji,Ishikado, Atsushi,Murakami, Nobutoshi,Yamahara, Johji,Matsuda, Hisashi
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p. 1815 - 1824
(2007/10/03)
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